I am not sure that highlighting would take longer than holding down delete, and that might depend on exactly how you are highlighting all messages. At the risk of asking the obvious, have you tried selecting just one message, holding down the 'shift' key and selecting the final message of a block of emails that you'd like to delete? It really almost couldn't be faster, especially if you're talking about watching emails delete one at a time as you hold down the delete key. Again, I might be asking the obvious, but I gotta make sure.
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soxmanMar 10 '12 at 1:09